The present invention relates to printing apparatus of the dot matrix type and more particularly to novel apparatus for selectively printing characters in one of a plurality of different font formats.
Line printers of the dot-matrix type are typically comprised of a print head movable across a paper document and capable of printing selected dot positions in a dot column. In one typical embodiment, the dot column has seven dot positions which may be selectively printed in any combination. Five adjacent dot columns collectively comprise a single alphanumeric character or other symbol thereby creating a 5.times.7 dot matrix wherein the selected printing of the 35 possible dot positions cooperatively form the desired alphanumeric character or other symbol. The print head is generally moved to the left-hand-most position of the paper document to begin the line of printing and then moves across the paper document at a substantially constant rate successively printing dot columns at selected ones of a plurality of uniformly spaced positions along a line until it reaches the right-hand end of the paper document thereby completing a line of print. The print head is then moved in the reverse direction back to the start of left-hand-most position and the paper document is advanced in readiness for printing the next line.
In one typical embodiment, for a size format of ten (10) characters per inch, a maximum of 80 characters may be printed along a line of 8 inch length. It is desirable to compress the width of each dot matrix character to enable printing of a larger amount of characters, typically 96 or 132 characters, along a line of the same length as set forth above, thereby realizing a significant reduction in printing paper usage.
It is also desirable to enable printing of a double-width elongated font of characters for special message, or "capital", characters said double width characters also being of the normal or compressed width. Also, no registration techniques presently in use include the capability of providing a selectable horizontal format.